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• Is it OK to write a constructor which does nothing?

  - by Roman

  To use methods of a class I need to instantiate a class. At the moment the class has not constructor (so I want to write it). But than I have realized that the constructor should do nothing (I do need to specify values of fields). In this context I have a question if it is OK to write constructor which does nothing. For example: public Point() { }

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• Javascript: Access the right scope "under" apply(...)

  - by Chau

  This is a very old problem, but I cannot seem to get my head around the other solutions presented here. I have an object function ObjA() { var a = 1; this.methodA = function() { alert(a); } } which is instantiated like var myObjA = new ObjA(); Later on, I assign my methodA as a handler function in an external Javascript Framework, which invokes it using the apply(...) method. When the external framework executes my methodA, this belongs to the framework function invoking my method. Since I cannot change how my method is called, how do I regain access to the private variable a? My research tells me, that closures might be what I'm looking for.

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• What is faster: write PHP code using "functions" or writing it as pure script?

  - by Ole Jak

  What is faster: writing PHP code using functions or writing it as pure script? So, as I see it Apache or any other server will create from PHP code using functions a pure script... I mean we had: function foo($a, $b){ return ($a + $b); echo foo(4, 5)} and Apache will turn it into something like: echo (5 + 4) Or will it?

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• Exposing members or make them private in Python?

  - by deamon

  Is there a general convention about exposing members in Python classes? I know that this is a case of "it depends", but maybe there is a rule of thumb. Private member: class Node: def __init__(self): self.__childs = [] def add_childs(self, *args): self.__childs += args node = Node() node.add_childs("one", "two") Public member: class Node2: def __init__(self): self.childs = [] node2 = Node2() node2.childs += "one", "two"

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• Implimenting Zend MVC for my existing site-first step?

  - by Joel

  Hi guys, OK-newbie question here. I'll try not to bombard SO with lots of questions-and hopefully this first one will show me the method I'll need to follow for subsequent conversions. I have a web-based calendar system that I developed, but it was coded for me procedurally (using PHP). I'm now working on learning OO and wanting to integrate this site into my localhost Zend Framework and slowly start converting parts to OO and the Zend Framework MVC process in particular. As I've said before, I understand that this will be a slow process, and when I'm done, I still probably won't have anything as OO friendly as if I had rewritten it from scratch, but I'd like to use this as a learning experience. So, I have dropped the whole site into my localhose/zend/Public folder, and everything is showing up great and linking to the database, etc. My question is-what would be the easiest first component to switch over to the MVC model? This site has a bit of everything-forms, login, authentication, some jQuery, etc. Can anyone point to a tutorial that would address what I'm trying to do? If indeed, a form would be one of the simpler things to switch, can someone walk me through those changes? Another idea is changing over all the header info, etc? Thanks for any pointers on where to start! EDIT: Also, I understand that SO is mainly for specific coding questions-I'm happy to share specific code, once I have an idea about which section to tackle first...

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• how to Clean up(destructor) a dynamic Array of pointers??

  - by Ahmed Sharara

  Is that Destructor is enough or do I have to iterate to delete the new nodes?? #include "stdafx.h" #include<iostream> using namespace std; struct node{ int row; int col; int value; node* next_in_row; node* next_in_col; }; class MultiLinkedListSparseArray { private: char *logfile; node** rowPtr; node** colPtr; // used in constructor node* find_node(node* out); node* ins_node(node* ins,int col); node* in_node(node* ins,node* z); node* get(node* in,int row,int col); bool exist(node* so,int row,int col); //add anything you need public: MultiLinkedListSparseArray(int rows, int cols); ~MultiLinkedListSparseArray(); void setCell(int row, int col, int value); int getCell(int row, int col); void display(); void log(char *s); void dump(); }; MultiLinkedListSparseArray::MultiLinkedListSparseArray(int rows,int cols){ rowPtr=new node* [rows+1]; colPtr=new node* [cols+1]; for(int n=0;n<=rows;n++) rowPtr[n]=NULL; for(int i=0;i<=cols;i++) colPtr[i]=NULL; } MultiLinkedListSparseArray::~MultiLinkedListSparseArray(){ // is that destructor enough?? cout<<"array is deleted"<<endl; delete [] rowPtr; delete [] colPtr; }

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• can I put my sqlite connection and cursor in a function?

  - by steini

  I was thinking I'd try to make my sqlite db connection a function instead of copy/pasting the ~6 lines needed to connect and execute a query all over the place. I'd like to make it versatile so I can use the same function for create/select/insert/etc... Below is what I have tried. The 'INSERT' and 'CREATE TABLE' queries are working, but if I do a 'SELECT' query, how can I work with the values it fetches outside of the function? Usually I'd like to print the values it fetches and also do other things with them. When I do it like below I get an error Traceback (most recent call last): File "C:\Users\steini\Desktop\py\database\test3.py", line 15, in <module> for row in connection('testdb45.db', "select * from users"): ProgrammingError: Cannot operate on a closed database. So I guess the connection needs to be open so I can get the values from the cursor, but I need to close it so the file isn't always locked. Here's my testing code: import sqlite3 def connection (db, arg): conn = sqlite3.connect(db) conn.execute('pragma foreign_keys = on') cur = conn.cursor() cur.execute(arg) conn.commit() conn.close() return cur connection('testdb.db', "create table users ('user', 'email')") connection('testdb.db', "insert into users ('user', 'email') values ('joey', 'foo@bar')") for row in connection('testdb45.db', "select * from users"): print row How can I make this work?

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• How would I associate a "Note" class to 4+ classes without creating lookup table for each associatio

  - by Gthompson83

  Im creating a project tasklist application. I have project, section, task, issue classes, and would like to use one class to be able to add simple notes to any object instance of those classes. The task, issue tables both use a standard identity field as a primary key. The section table has a two field primary key. The project table has a single int primary key defined by the user. Is there a way to associate the note class with each of these without using a seperate lookup table for each class? I'm not so sure my original idea is a decent way to implement this. I considered the following (each variable mapping to a field n the notes table. Private _NoteId As Integer Private _ProjectId As Integer Private _SectionId As Integer Private _SectionId2 As Integer Private _TaskId As Integer Private _IssueId As Integer Private _Note As String Private _UserId As Guid Then I would be able to write seperate methods (getProjectNotes, getTaskNotes) to get notes attached to each class. I started writing this a few weeks ago but got pulled away before i could finish. When revisiting this code today my first thought "this is retarded". Thoughts on drawbacks to this design?

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• Is it true that in most Object Oriented Programming Languages, an "i" in an instance method always r

  - by Jian Lin

  In the following code: <script type="text/javascript"> var i = 10; function Circle(radius) { this.r = radius; this.i = radius; } Circle.i = 123; Circle.prototype.area = function() { alert(i); } var c = new Circle(1); var a = c.area(); </script> What is being alerted? The answer is at the end of this question. I found that the i in the alert call either refers to any local (if any), or the global variable. There is no way that it can be the instance variable or the class variable even when there is no local and no global defined. To refer to the instance variable i, we need this.i, and to the class variable i, we need Circle.i. Is this actually true for almost all Object oriented programming languages? Any exception? Are there cases that when there is no local and no global, it will look up the instance variable and then the class variable scope? (or in this case, are those called scope?) the answer is: 10 is being alerted.

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• Can I refer to an object in its constructor?

  - by Roman

  Can I do the following? public Manager(String userName) { game = new Game(userName); game.addManager(this); } The problem is that I refer to an object (this) in its constructor (before it was actually created).

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• Which is the correct design pattern for my PHP application?

  - by user1487141

  I've been struggling to find good way to implement my system which essentially matches the season and episode number of a show from a string, you can see the current working code here: https://github.com/huddy/tvfilename I'm currently rewriting this library and want a nicer way to implement how the the match happens, currently essentially the way it works is: There's a folder with classes in it (called handlers), every handler is a class that implements an interface to ensure a method called match(); exists, this match method uses the regex stored in a property of that handler class (of which there are many) to try and match a season and episode. The class loads all of these handlers by instantiating each one into a array stored in a property, when I want to try and match some strings the method iterates over these objects calling match(); and the first one that returns true is then returned in a result set with the season and episode it matched. I don't really like this way of doing it, it's kind of hacky to me, and I'm hoping a design pattern can help, my ultimate goal is to do this using best practices and I wondered which one I should use? The other problems that exist are: More than one handler could match a string, so they have to be in an order to prevent the more greedy ones matching first, not sure if this is solvable as some of the regex patterns have to be greedy, but possibly a score system, something that shows a percentage of how likely the match is correct, i'd have no idea how to actually implement this though. I'm not if instantiating all those handlers is a good way of doing it, speed is important, but using best practices and sticking to design patterns to create good, extensible and maintainable code is my ultimate priority. It's worth noting the handler classes sometimes do other things than just regex matching, they sometimes prep the string to be matched by removing common words etc. Cheers for any help Billy

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• How do I organize C# classes that inherit from one another, but also have properties that inherit from one another?

  - by Chris

  I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this: public abstract class Venue { public int Id { get; set; } public string Name { get; set; } public virtual Company Company { get; set; } public virtual ICollection<VenuePart> VenueParts { get; set; } } A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart: public class GolfCourseVenue { public string Slope { get; set; } public virtual ICollection<HoleVenuePart> Holes { get; set; } } In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type. My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific. I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.

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• Java debug error

  - by ivor

  Hello, I wonder if anyone can help - I have this error showing recently when debugging in eclipse - what doe it mean by resource, an imported package or the location of some java files ? Can't find resource for bundle sun.awt.resources.awt, key AWT.EventQueueClass MissingResourceException (id =45) Thanks

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• how to implement a callback in runnable to update other swing class

  - by wizztjh

  I have a thread like this public class SMS { class Read implements Runnable { Read(){ Thread th = new Thread(this); th.start(); } @Override public void run() { // TODO Auto-generated method stub while (true){ Variant SMSAPIReturnValue = SMSAPIJava.invoke("ReadSMS"); if (SMSAPIReturnValue.getBoolean()){ String InNumber = SMSAPIJava.getPropertyAsString("MN"); String InMessage = SMSAPIJava.getPropertyAsString("MSG"); } } } } } How do I update the message to another GUI class in the same package(I understand how to put nested class to another package ....). Should I implement a callback function in SMS class? But how? Or should I pass in the Jlabel into the class?

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• exclude private property from print_r or object?

  - by Hailwood

  Basically I am using Code Igniter, and the Code Igniter base class is huge, when I print_r some of my objects they have the base class embedded inside them. this makes it a pain to get the information I actually wanted (the rest of the properties). So, I am wondering if there is a way I can hide, or remove the base class object? I have tried clone $object; unset($object->ci); print_r($object); but of course the ci property is private. the actual function I am using for dumping is: /** * Outputs the given variables with formatting and location. Huge props * out to Phil Sturgeon for this one (http://philsturgeon.co.uk/blog/2010/09/power-dump-php-applications). * To use, pass in any number of variables as arguments. * Optional pass in "true" as final argument to kill script after dump * * @return void */ function dump() { list($callee) = debug_backtrace(); $arguments = func_get_args(); $total_arguments = count($arguments); if (end($arguments) === true) $total_arguments--; echo '<fieldset style="background: #fefefe !important; border:2px red solid; padding:5px">'; echo '<legend style="background:lightgrey; padding:5px;">' . $callee['file'] . ' @ line: ' . $callee['line'] . '</legend><pre>'; $i = 0; foreach ($arguments as $argument) { //if the last argument is true we don't want to display it. if ($i == ($total_arguments) && $argument === true) break; echo '<br/><strong>Debug #' . (++$i) . ' of ' . $total_arguments . '</strong>: '; if ((is_array($argument) || is_object($argument)) && count($argument)) { print_r($argument); } else { var_dump($argument); } } echo '</pre>' . PHP_EOL; echo '</fieldset>' . PHP_EOL; //if the very last argument is "true" then die if (end($arguments) === true) die('Killing Script'); }

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• How can I use Object Oriented Javascript to interact with HTML Objects

  - by Steve

  I am very new to object orientated javascript, with experience writing gui's in python and java. I am trying to create html tables that I can place in locations throughout a webpage. Each html table would have two css layouts that control if it is selected or not. I can write all of the interaction if I only have one table. It gets confusing when I have multiple tables. I am wondering how to place these tables throughout a blank webpage and then access the tables individually. I think I am having trouble understanding how inheritance and hierarchy works in javascript/html. NOTE: I am not asking how to make a table. I am trying to dynamically create multiple tables and place them throughout a webpage. Then access their css independently and change it (move them to different locations or change the way the look, independently of the other tables).

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• Multiple Inheritance Debates II: according to Stroutroup

  - by asksuperuser

  I know very well about the traditional arguments about why Interface Inheritance is prefered to multiple inheritance, there has been already a post here : http://stackoverflow.com/questions/191691/should-c-include-multiple-inheritance But according to Stroutroup the real reason why Microsoft and Sun decided to get rid off multiple inheritance is that they have vested interest to do so: instead of putting features in the languages, they put in frameworks so that people then become tied to their platform instead of people having the same capability at a language standard level. What do you think ?

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• where are the frameworks for creating libraries?

  - by fayer

  whenever i create a php library (not a framework) i tend to reinvent everything everytime. "where to put configuration options" "which design pattern to use here" "how should all the classes extend each other" and so on... then i think, isn't there a good library framework to use anywhere? it's like a framework for a web application (symfony, cakephp...) but instead of creating a web application, this framework will help coder to create a library, providing all the standard structure and classes (observer pattern, dependency injection etc). i think that will be the next major thing if not available right now. in this way there will be a standard to follow when creating libraries, or else, it's like a djungle when everyone creates their own structure, and a lot of coders just code without thinking of reusability etc. there isn't any framework for creating libraries at the moment? if not, don't u agree with me that this is the way to do it, with a library framework? cause i am really throwing a lot of time (weeks!) just thinking about how to organize things, both in code and file level, when i should just start to code the logic. share your thoughts!

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• "Abstract static" method - how?

  - by polyglot

  There are already several SO questions on why there is not abstract static method/field as such, but I'm wondering about how one would go about implementing the following psuedo-code: class Animal { abstract static int getNumberOfLegs(); // not possible } class Chicken inherits Animal { static int getNumberOfLegs() { return 2; } class Dog inherits Animal { static int getNumberOfLegs() { return 4; } Here is the problem: Assuming that I want make sure that every class that inherits Animal to contain getNumberOfLegs() method (i.e. almost like an interface, except I do want the abstract class to implement several methods that are common to all child classes, hence pure interface does not work here). getNumberOfLegs() obviously should be a static method (assuming that in a perfect world we dont' have crippled chicken and dogs so getNumberOfLegs is not instance-dependent). Without an "abstract static" method/field, one can either leave the method out from Animal class, then there is the risk that some child class do not have that method. Or one can make getNumberOfLegs an instance method, but then one would have to instantiate a class to find out how many legs that animal has - even though it is not necessary. How do one usually go about implementing this situation?

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• mysqli insert into database

  - by Simon

  Hello all i have this script and i will not insert into the database and i get no errors :S, do you know what it is? function createUser($username, $password) { $mysql = connect(); if($stmt = $mysql->prepare('INSERT INTO users (username, password, alder, hood, fornavn, efternavn, city, ip, level, email) VALUES (?,?,?,?,?,?,?,?,?,?)')) { $stmt->bind_param('ssssssssss',$username,$password, $alder, $hood, $fornavn, $efternavn, $city, $ip, $level, $email); $stmt->execute(); $stmt->close(); } else { echo 'error: ' . $mysql->error; }

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• Type hinting and optional attributes in PHP

  - by Álvaro G. Vicario

  I have a class method that deals with dates: public function setAvailability(DateTime $start, DateTime $end){ } Since item availability can have lower limit, upper limit, both or none, I'd like to make setAvailability() accept NULL values as well. However, the NULL constant violates the type hinting: $foo->setAvailability(NULL, $end); triggers: Catchable fatal error: Argument 1 passed to Foo::setAvailability() must be an instance of DateTime, null given And, as far as I know, I cannot have a DateTime instance with no value. (Can I?) For a reason I cannot grasp, this seems to work: public function setAvailability(DateTime $start=NULL, DateTime $end=NULL){ } ... $foo->setAvailability(NULL, $end); But it looks like a hack that works by pure chance. How would you deal with unset dates in PHP classes?

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• how to make objects globally accessible?

  - by fayer

  i have this code: class IC_Core { /** * Database * @var IC_Database */ public static $db = NULL; /** * Core * @var IC_Core */ protected static $_instance = NULL; private function __construct() { } public static function getInstance() { if ( ! is_object(self::$_instance)) { self::$_instance = new self(); self::initialize(self::$_instance); } return self::$_instance; } private static function initialize(IC_Core $IC_Core) { self::$db = new IC_Database($IC_Core); } } but when i wanna access IC_Database with: $IC = IC_Core::getInstance(); $IC->db->add() // it says that its not an object. i think the problem lies in self::$db = new IC_Database($IC_Core); but i dont know how to make it work. could someone give me a hand=) thanks!

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• Unable to Get values from Web Form to a PHP Class to Display

  - by kentrenholm

  I am having troubles getting the value from my variables submitted via a web form using a PHP class file. Here is my structure of the web page: Order Form Page Process.php Page Book.php Page I can easily get the user data entered (on Order Form Page), process, and display it on the Process.php page. The issue is that I must create a Book class and print the details of the data using the Book class. I have an empty constructor printing out "created" so I know my constructor is being called. I also am able to print the word "title" so I know I can print to the screen by using the Book class. My issue is that I can't get values in my variables in the Book class. Here is my variable declaration: private $title; Here is my printDetails function: public function printDetails () { echo "Title: " . $this->title . "<br />"; } Here is my new instance of the book class: $bookNow = new book; Here are my get and set functions: function __getTitle($title) { return $this->$title; } function __setTitle($title,$value) { $this->$title = $value; } I do have four other variables that I'm looking to display as well. Each of those have their own variable declaration, a line in printDetails, and their own setter and getter. Lastly, I also have a call to the Book class in my process PHP. It looks like this: function __autoload($book) { include $book . '.php'; } $bookNow = new book(); Any help, much appreciated. It must be something so very small (I'm hoping).

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• OO C++ - Virtual Methods

  - by Phorce

  Just a really quick question here. I'm using virtual functions to read in from a text file. Now, it's virtual because in one aspect I want the values to be normalised, and, in the other respect I don't want them to be normalised. I have tried to do this: bool readwav(string theFile, 'native'); So in theory, if the 'native' is used, this method should be called, however, if 'double' is called then a different version of the method is called. Same for if the value is empty, it should just perform the native option. First question, why doesn't the declaration above work? Also, is this the best route to go down? Or, would it be better to have just one class method that switches between the options. Thanks :)

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• Session State Anti-Pattern

  - by Curiosity

  I know the SOLID principles and other design patterns fairly well and have been programming for some time now - seeing many a bit of code throughout the years. Having said that, I'm having trouble coming up with a name to give the pattern, or lack thereof, to bits of code I've been dealing with at a current engagement. The application is an ASP.NET C# WebForms application, backed by a SQL Server/Mainframe backend (more mainframe than backend) and it's riddled with Session State properties being accessed/mutated from multiple pages/classes. Accessing/mutating global variables/application state was usually shunned upon while I was in school. Apparently the creators of this magnificent application didn't think it was such a bad idea. Question: Is there a name for such a pattern/anti-pattern that relies so heavily on Session State? I'd like to call the pig by its name ...

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